HTN: Fiber (2007)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To test whether a diet designed for weight loss that contained oats would yiled greater improvements in blood pressure and lipid profiles than a similar diet without oats.
Inclusion Criteria:
  • BMI of 20 to 35 and weight stable
  • Aged 18 to 30 years or 60 to 75 years
  • SBP under 150mm Hg and DBP under 90mm Hg
  • Healthy, based on physical exam and blood tests.
Exclusion Criteria:
  • Smoking
  • Takng medication known to influence weight or BP
  • History of eating disorders
  • History of acute or chronic disease
  • Strenuous exercise for at least one hour per day
  • Habitual consumption of over 30g per day of alcohol.
Description of Study Protocol:


  • Subjects were recruited for a dual purpose of determining the effects of hypocaloric diets with and without oats on BP and blood lipids, as well as for measures of energy regulation
  • The influence of varying BMI and age (a younger group and an older group) was compared.
  • Randomized controlled trial of two phases
  • The initial two-week weight-maintenance phase was followed by a six-week weight-loss phase.

Blinding Used

None mentioned.


  • All food and beverage was provided at the Medical Research Unit
  • During phase one, all subjects received the control diet with energy intake to maintain weight
  • In phase two, subjects received a diet to maintain energy balance minus 4.2mJ per day with the exception of seven subjects, who had a decrease of just 3.3mJ to 3.7mJ per day
  • The Oats Group received the hypocaloric diet containing 45g dry weight of oats (approximately 1.5 servings of oatmeal) and the Control Group received the hypocaloric diet without added oats
  • The oats for the Oat Group were consumed as hot cereal or incorporated into foods at all meals and snacks

Statistical Analysis

  • Student's T-test for independent samples was used to compare the groups at baseline and to compare mean change scores between the two groups
  • ANCOVA was used to adjust differences for age and gender and to assess interactions of tratment with diet and gender.
Data Collection Summary:

Timing of Measurements

BP was measured at least four times per week during the study period, with initial and final SBP and DBP defined as averages of each in week two of phase one and week eight (end of phase two). 

Dependent Variables

  • SBP and DBP measured after quiet sitting with a sphygmomanometer
  • Serum lipids, insulin sensitivity and fasting glucose.

Independent Variables

  • Control Group: Hypocaloric diet of mixed foods plus a multivitamin without added minerals
  • Oats Group: Hypocaloric diet of mixed foods plus multivitamin plus 45g oats per day.
Description of Actual Data Sample:

Initial N: 43 (20 men); 22 in Oats Group, 21 in Control Group

Attrition (final N): 43


  • Young subjects in Control Group (N=12): 19 to 30 years of age
  • Young subject in Oats Group (N=12): 22 to 30 years of age
  • Older subjects in control group (N=9): 64 to 72 years
  • Older subjects in treatment group (N=10): 65 to 78 years.


Not discussed.

Anthropometrics: Baseline Measures, Mean±SD


Control Group

Oats Group

Weight, kg






Body Fat, g/100g weight





Summary of Results:

BP at Baseline (Phase 1) and After Treatement (Phase 2); P-Value is for Difference Between Groups

  Control Group Oats Group P-Value
Phase 1 SBP, mmHg 118±15 117±9 >0.05
Phase 1 DBP, mmHg 70±8 72±6 >0.05
Phase 2 minus Phase 1SBP, mmHg -1±10 -6±7 <0.05
Phase 2 minus Phase 1DBP, mmHg -3±5 -4±6 >0.05


Daily Nutrient Intake for Select Nutrients from Diet


Control Phase 1

Control Phase 2

Oats Phase 1

Oats Phase 2

Total fiber
Soluble fiber
3,380±713 mg

[Note: The difference in total fiber and soluble fiber intake between groups was less than four grams per day and the difference in calcium intake varied by 103mg.  No P-values given between groups.]

Other Findings

  • Mean baseline blood pressures were in the normal range. Within each group, DBP decreased from phase 1 to phase 2 (shown above, P=0.0001). When controlling for initial BP, initial BMI and weight lost, the oat diet had a greater effect than the control diet on SBP (P=0.026), but not on DBP (P=0.8). Thus, this decrease in SBP was independent of weight loss.
  • There were no differences between the groups in age, initial weight, BMI,or body fat percentage. Both groups experienced a similar weight loss during phase two: Control, -4.0±1.1kg; Oat Group, -3.9±1.6kg; P=0.8.
  • The oat diet resulted in greater decreases in total cholesterol and LDL-C (P=0.003 and P=0.008, respectively).
Author Conclusion:
A hypocaloric diet containing oats consumed for six weeks resulted in greater improvements in SBP and lipid profile than a hypocaloric diet without oats.
Funding Source:
Government: USDA, NIH
Quaker Oats
Food Company:
Reviewer Comments:
  • Another purpose of the study was to measure energy regulation in healthy adults with comparisons in older and younger groups
  • Control and treatment groups received the same foods with the exception of oats added to the treatment group diet
  • Subjects were instructed to maintain their usual activity level throughout the study
  • Compliance was measured by weight loss.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes